Former great Ian Chappell said Thursday that Australia need key all-rounder Shane Watson for the second Test against South Africa, dismissing as "ridiculous" suggestions he was not a top-six batsman.

Watson sat out the first Gabba Test with a calf injury and is no certainty for next week's match-up with the world number one Proteas, with selectors warning that an inability to bowl would count significantly against him.

The Australians came out of the first of three Tests with an edge over the South Africans in the drawn game. But they must win the series to wrest the world number one ranking from their rivals.

Chappell, a former Test captain and top-order batsman, said Watson should make the cut regardless of whether he can bowl.

"If I'm a selector picking the Australia XI and Shane Watson is not in the best six batsmen, I've been watching a different game," Chappell told the Australian Associated Press Thursday.

"If Watson is fit to play and they don't pick him as a batsman, I find that strange. He has proven himself as a batsman."

Chappell said omitting Watson, prolific for Australia with both bat and ball in all formats recently, could leave the team exposed to a strong South African pace attack. The first three wickets fell cheaply in Brisbane.

Australia's top three of Ed Cowan, David Warner and Watson's replacement at the Gabba Rob Quiney only have 19 Test caps between them and Chappell said Watson's 35-cap experience could prove vital to fending off the Proteas.

"Australia have taken a strong psychological edge away from the first Test, but South Africa can turn that around with their bowling," said Chappell.

"If Shane can't bowl, that is not the major consideration," he added.

"You want to pick the best team to give you the best chance to win the game and that means Shane Watson should be there, whether he can bowl or not."

Warner also threw his support behind Watson.

"Just having him in the team, the class of player he is, brings a lot of experience to the team," Warner told reporters.